Sheet feed method and apparatus

ABSTRACT

The present disclosure relates to a sheet feeding method and apparatus by which sheets of material can be fed, one at a time, into a processing or finishing machine. The present disclosure includes a continuously moving feed means that is driven and moves continuously at line speed. The continuously moving feed means are provided with vacuum means to pull the sheet into engagement with the feed means. A feed plate is provided for movement between a lowered, feed position in which the feed plate is lowered to a position below the feed means and a raised, no feed position in which the feed plate is raised to a position just above the feed means to prevent a sheet from being fed. In one embodiment, the movement of the feed plate is provided and controlled via a rotating, profiled eccentric which is driven by a servo electric motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on U.S. Provisional Patent Application Ser. No. 60/827,900 filed on Oct. 3, 2006. The priority of this provisional application is hereby claimed and is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a sheet feed method and apparatus and more specifically to a sheet feed method and apparatus for feeding a sheet of material from a stack of sheets to a further processing machine accurately at high speeds. The present invention has particular applicability to the feeding of sheets such as cardboard, paperboard and corrugated box blanks, among other materials.

DESCRIPTION OF THE PRIOR ART

A variety of industries require delivering sheets of material, one at a time, from a stack of sheets to a destination for further processing. In all of these applications, speed and accuracy are highly desired. One application of current sheet feeders involves delivering cardboard, paperboard or corrugated box blanks from a stack of such blanks to a further processing or finishing machine. In such application, it is desirable for the blanks to be fed accurately and at high speed, as many as six blanks per second or more.

Current machines for this application utilize either a series of narrow belts or rows of rollers that are driven by an electrical motor through a special sinusoidal output gear box. These belts include vacuum means which function to pull the blank or sheet from the bottom of the stack into engagement with the belts or rollers and to maintain such engagement during the feeding process. Associated with the belts or rollers is a feed plate which supports the bottom blank or sheet in a position just above the belts or rollers until the blank or sheet is fed.

During the sheet feeding process of these current machines, the gear box ramps the belts or rollers to a stop. As this occurs, the feed plate is lowered to allow the bottom sheet to be pulled into engagement with the belts or rollers by the vacuum means. The belts or rollers are then ramped up virtually instantaneously to line speed. This pulls the bottom sheet from the stack and feeds it to its desired destination. As the first sheet is fed, the feed plate then moves upwardly to prevent feeding of the next sheet until the belts or rollers are again ramped to a stop. The process is then repeated for the next sheet.

Accordingly, current sheet feeding machines utilize belts or rollers which are stopped and started repeatedly (as often as six times a second or more) together with corresponding up and down movement of a feed plate. Both of these movements are produced and controlled by an extremely complex and expensive sinusoidal output gear box which drives both the belt or roller and the feed plate movements.

Current sheet feeding machines have several limitations. First, because of their complexity, they are expensive and their manufacture and maintenance is critical. Second, because the cycle of the belt/roller and feed plate movements is manufactured into the gear box, the flexibility of these machines relative to handling varying sizes of blanks or sheets, etc. is limited. Thirdly, for this same reason, the accuracy is limited in that there is no means to adjust or correct for a sheet which is delivered before or after the time it should be.

Accordingly, there is a need in the art for a sheet feeding method and apparatus which addresses the limitations of the prior art.

SUMMARY OF THE INVENTION

The present invention is directed to a sheet feeding method and apparatus by which sheets of material such as, but not limited to, cardboard, paperboard and corrugated box blanks or sheets can be fed, one at a time, into a processing or finishing machine. In accordance with the present invention, these sheets can be fed accurately at a selectable repeat distance and at very high speeds, up to six sheets per second or more. Further, the system is capable of feeding sheets from the bottom of a stack of sheets as is conventionally done, or from the top of a stack of sheets, or from a stack of sheets sitting at any angle.

More specifically, the apparatus of the present invention includes a continuously moving feed means in the form of a series of narrow belts or rollers that are driven and move continuously at line speed. Preferably these belts or rollers are also continuously driven at a constant or substantially constant speed. The belts or rollers are provided with vacuum means to pull the sheet into engagement with the belt. The belts or rollers can be driven at line speed by a standard electrical drive such as an AC motor, or optionally with a servo electric drive for better accuracy.

A feed plate is provided for movement between a lowered, feed position in which the feed plate is lowered to a position below the feed belt and a raised, no feed position in which the feed plate is raised to a position just above the feed belt to prevent a sheet from being fed. When the feeding of a sheet is desired, the feed plate is lowered to just below the feed belt to allow the bottom sheet to engage the continuously moving feed belts or rollers and thus be fed into a conveyor or other delivery means and ultimately to a processing or finishing machine. After the sheet is fed, the feed plate is raised to its no feed position, at which time a further feed cycle can be commenced by again lowering the feed plate. In the preferred embodiment, the movement of the feed plate is provided and controlled via a rotating, profiled eccentric which is driven by a servo electric motor.

Accuracy of the sheet feeding method and apparatus of the present invention can be improved by providing a detection mechanism such as a photoelectric sensor to detect the position of each sheet being fed and then adjusting the position of such sheet, if necessary, through a servo driven nip roller and/or servo driven belts or rollers.

Accordingly, it is an object of the present invention to provide an improved sheet feeding method and apparatus.

Another object of the present invention is to provide a sheet feeding method and apparatus having particular applicability to feeding blanks or sheets from a stack of such blanks or sheets to a processing or finishing machine.

A further object of the present invention is to provide a sheet feeding method and apparatus in which the feed belt or rollers are driven continuously during the feeding process.

A still further object of the present invention is to provide a sheet feeding method and apparatus which is extremely accurate and in which the sheets can be fed at high speeds.

These and other object of the present invention will become apparent to the drawings, the description of the preferred embodiment and the appended claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side schematic illustration of the sheet feed apparatus in accordance with the present invention.

FIG. 2 is a side schematic illustration similar to FIG. 1, except that the sheets are fed from the top of a stack.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND METHOD

The present invention is directed to a sheet feed method and apparatus for feeding a sheet material from a stack of sheets. The present invention has particular applicability to the feeding of sheets such as cardboard, paperboard and corrugated box blanks from a stack of such blanks. Accordingly, the preferred embodiment will be described with respect to a sheet feeder for feeding blanks such as corrugated container blanks or sheets into a processing or finishing machine. Such processing or finishing machines are well known in the art and may include machines for folding and/or gluing the cardboard blanks, machines for cutting the cardboard blanks and machines for printing onto the cardboard blanks, among others. Throughout the application, unless otherwise noted, the term “sheet” shall include, without limitation, a cardboard, paperboard or corrugated box blank.

The sheet feeding apparatus of the present invention includes many of the same functional components as currently existing sheet feeders including, among other things, a plurality or series of feed belts or rollers, a reciprocating feed plate, a feed gate, a vacuum means and a nip roller. Accordingly, such components and their general function are known in the art.

A principal difference between prior art sheet feed systems and the feed system of the present invention is that in prior art sheet feed systems, the feed belts or rollers are repeatedly stopped and started each time a sheet is fed, in coordination with a reciprocating feed plate. In these prior systems, the movements of the feed belts or rollers and the feed plate are provided and controlled by a complex and expensive sinusoidal or other gear box.

In contrast, the sheet feed system in accordance with the present invention provides a series of feed belts or rollers which are driven continuously at line speed in coordination with a reciprocating feed plate. Thus, the sheet feed system of the present invention, among other things, eliminates the complex and expensive gear box of current systems.

The sheet feed system 10 of the present invention is designed to feed sheets such as, but not limited to, corrugated blanks, one at a time, from a stack of such sheets. As shown in FIG. 1, the apparatus 10 is positioned below a stack 13 of sheets and is designed to feed sheets from the bottom, such as the sheet 17, one at a time in the direction of the arrow 23. The stack of sheets other than the bottom sheet 17 are prevented from being prematurely fed by the feed gate 27. Specifically, the feed gate 27 is designed to adjust vertically to allow just enough clearance along its bottom edge to allow a single sheet to pass under.

The sheet feed apparatus 10 of the preferred embodiment includes a feed belt vacuum chamber 11 and an associated vacuum generator 12. Operatively associated with, and at least partially positioned within the vacuum housing 11, is a feed belt means 14, a feed plate 15 and a feed plate drive means 16.

In the preferred embodiment, the feed belt means 14 includes a plurality or series of laterally spaced feed belts 18 which are carried by a plurality or series of front feed belt rollers or pulleys 19 and a plurality or series of rear feed belt rollers or pulleys 20. As is known in the art, spacers may be provided between the laterally spaced belts. As shown, the feed belts 18 extend around and between the rollers 19 and 20, with the top run of the belts 18 positioned just above the top portion 21 of the vacuum housing 11. The lower run of the feed belts passes through the vacuum housing 11. The belts 18 are provided with a plurality of holes or slots on and/or along side to allow a vacuum from within the chamber 11 to pull the bottom sheet 17 into engagement with the belt 18 during a feed cycle.

In the preferred embodiment, the front feed rollers 19 are supported on a front roller shaft 22, while the rear belt rollers are mounted on a rear roller shaft 25. In most cases, and as shown in FIG. 1, the top run or portion of the belt 18 exposed to the bottom sheet 17 is less, and in some cases significantly less, than the length of the sheets being fed. A pulley 24 is connected with the shaft 22 and is driven via the feed belt drive motor 26 and the endless drive belt 28. The feed belt drive motor 26 includes an output shaft 30 and a drive pulley 31 connected with the shaft 30. The drive belt 28 extends between and around the pulleys 24 and 31 so that rotational movement of the drive motor 29 and shaft 30 drives the feed belts 18 through the pulleys 31 and 24 and the drive belt 28. During operation, the motor 26 rotates and thus the belt 18 moves continuously in a counter clockwise direction as viewed in FIG. 1 to feed the sheets in the direction of the arrow 23.

In the preferred embodiment, the drive motor 26 is a motor which is capable of continuously driving the feed belts 18 at line speed. Preferably, the motor is also capable of driving the belts 18 at a constant or substantially constant speed. Accordingly, the motor 26 may be a common, continuously driven AC electric motor or a continuously driven servo motor. If greater sheet feed accuracy is desired, the motor 26 may be a servo driven motor. A servo motor, in combination with sheet position detecting means such as the photo electric sensor 45, enables the speed of the servo motor to be adjusted slightly to compensate for a sheet which is out of position and thus provides a sheet feed system with improved accuracy.

Although the preferred embodiment contemplates a plurality or series of laterally spaced feed belts 18, it is contemplated that a plurality or series of feed rollers can be utilized as well. Such laterally spaced belts and rollers are well known in the art.

The feed plate 15 is comprised of laterally spaced feed plate sections interleaved between the series of feed belts or rollers 18. In the preferred embodiment, the feed plate 15 or each feed plate section includes a forward pivot portion 32 pivotally mounted relative to the front roller shaft 22 and a rearward feed section 34. A top surface 35 of the feed plate 15 or each feed plate section is designed for engagement with the bottom surface of the bottom sheet 17 during the no feed portion of a feed cycle. Accordingly, during the feed portion of a feed cycle, the top surface 35 is at or slightly below the top surface of the belts 18. During the no feed portion of a feed cycle, the surface 35 is raised slightly above the top surface of the belts 18 to preclude engagement between the belts 18 and the bottom sheet 17.

A reciprocating motion transmission member 36 is operatively connected between the feed plate section 34 and a profiled eccentric cam 38 of the reciprocating means 16 to provide reciprocating “feed” and “no feed” movements of the plate 15. The cam 38 is rotatably supported on the shaft 39 and includes an outer eccentric profiled cam surface which engages a portion of the transmission member 36. An eccentric cam drive includes a drive motor 40, an output shaft 41 and a drive pulley 42. A drive belt 44 extends around and between the pulleys 42 and 37 so that rotation of the output shaft 41 rotates the eccentric cam 38 via the pulleys 42 and 37 and the drive belt 44. During the feed cycle, the drive motor 40 drives the eccentric cam 38 which in turn engages the member 36 causing reciprocal movement of the feed plate section 34 and thus the top surface 35 of the feed plate 15. During this movement, the feed plate section 34, and thus its top surface 35, moves reciprocally as shown by the arrow 33 between a lowered, “feed” position in which the surface 35 is at or slightly below the top surface of the feed belts 18 and a raised, “no-feed” position in which the surface 35 is slightly above the top of the feed belts 18. In the preferred embodiment, the motor 40 is preferably a servo electric motor and the reciprocating motion is controlled by such motor and the profile of the eccentric cam 38.

Although the preferred embodiment contemplates a structure in which reciprocal movement of the feed plate 15 is provided by the cam means which pivots the plate 15 about the pivot 32, this reciprocal movement could also be provided linearly vertically by a cam or other reciprocating means.

A nip roller assembly comprised of a flexible nip roller 48 is mounted for rotation about a nip roller shaft 49 driven by a nip roller motor. As shown, the nip roller assembly is positioned above a forward end of the feed belt 18 and forward of the feed gate 27. A gap is provided between the feed belt 18 and the periphery of the nip roller 48. This gap is slightly smaller than the thickness of the sheet being fed, thereby enabling the flexible nip roller 48 to maintain sufficient pressure against the sheet being fed to keep the sheet moving at the line speed of the feed belt 18. Such pressure, however, should not be sufficient to alter the speed or position of the sheet being fed independently of the feed belt 18. Accordingly, the nip roller is designed to rotate continuously at line speed approximating the continuous line speed of the belt 18.

In one embodiment, the nip roller assembly may be driven at line speed by a common AC electric motor. In a second embodiment, however, the nip roller assembly may be driven by a servo electric motor. In general, a servo driven nip roller assembly usually has applicability only with a servo driven drive belt assembly and a sheet position detecting means such as the photo electric sensor 45. In the preferred embodiment, the photoelectric sensor 45 or other position detecting means functions to locate the actual position (via detecting a leading edge, a trailing edge or some other sheet marker) of a sheet being fed, and comparing such actual position with the position where such sheet should be. A servo driven feed belt system, particularly in combination with a servo driven nip roller, can be used to more accurately control the position of a sheet being fed. Although it is possible for the position of a sheet to be adjusted with only a servo driven feed belt system, improved accuracy can be achieved when both the feed belt system and the nip roller assembly are servo driven in unison. By combining a servo driven feed belt system (or servo driven feed belt and nip roller) with a sheet detection means such as the sensor 45, the actual position of a sheet being fed can be compared with its desired position so that a position adjustment can be made if necessary, either by temporarily speeding up the feed belt (or feed belt and nip roller) and/or by temporarily slowing the feed belt (or feed belt and nip roller).

The system of FIG. 1 is designed to feed sheets from the bottom of a stack 13 of sheets one at a time. Such system can, however, also function to feed sheets from the top of a stack setting at any angle by rotating the system of FIG. 1 180 degrees (or other angle). When rotated 180 degrees, the sheets are fed from the top of the stack 13 as shown in FIG. 2 rather than the bottom of the stack 13 as shown in FIG. 1. In the embodiment of FIG. 2, the operational elements of the sheet feeding apparatus are the same as those described above with respect to FIG. 1. The principal difference in the system of FIG. 2 is that an upward force 50 is exerted on the bottom of the stack which approximates the gravitational force exerted by the stack 13 of FIG. 1 against the bottom sheet 17. If the stack systems are positioned at an angle other than 180 degrees from that of FIG. 1, the force 50 is adjusted accordingly.

Having described the structure of the sheet feed system of FIGS. 1 and 2, its method of operation can be understood as follows. Initially, in the start position, the feed plate 15 is in its raised, no-feed position, the feed belts 18 (and the nip rollers 48 if provided) are running continuously at line speed and the vacuum generator 12 is pulling a vacuum. When the feed plate 15 is in this initial start position, the vacuum is pulling the bottom sheet 17 flat against engagement with the top surface 35 of the feed plate 15.

As the feed cycle enters the feed portion of the cycle, the feed plate 15 is lowered as quickly as possible via the servo driven reciprocating means. When this occurs, the vacuum in the vacuum chamber pulls the bottom sheet 17 into engagement with the feed belt 18 and begins feeding the sheet. The distance the sheet is fed depends upon the length of the sheet. When the trailing edge of the sheet reaches the feed belt, the feed plate is raised to avoid feeding a second sheet. In the preferred embodiment, and if a position detecting means such as the photoelectric sensor 45 is utilized, the sensor detects whether the fed sheet is in the correct position before allowing the next sheet to feed. The feed plate 15 will remain in its raised, no-feed position until the timing is correct for the next sheet to be fed.

If the feed belt is driven by a servo electric drive and if the photoelectric sensor 45 or other sheet position detecting means detects an incorrect position of the fed sheet, the error in the sheet position can be eliminated by speeding up or slowing down the servo driven feed belt system and the servo driven nip roller assembly, if provided.

If a position means and servo driven belt system are not provided, the feed belt 18 simply rotates continuously, at constant or substantially constant speed, with the feeding of the sheets being controlled substantially by the reciprocating feed plate 15.

Although the description of the preferred embodiment has been quite specific, it is contemplated that various modifications could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the scope of the present invention be dictated by the appended claims rather than by the description of the preferred embodiment. 

1. A sheet feed apparatus for feeding sheets, one at a time, from a stack of sheets, the apparatus comprising: a continuously driven feed belt/roller assembly and a driven feed plate moveable between a feed position and a no-feed position.
 2. The sheet feed assembly of claim 1 wherein said belt/roller assembly is servo driven.
 3. The sheet feed assembly of claim 1 including a sheet position detecting means.
 4. The sheet feed assembly of claim 3 wherein said sheet position detecting means is a photo electric sensor.
 5. The sheet feed assembly of claim 2 including a sheet position detecting means.
 6. The sheet feed assembly of claim 5 wherein said sheet position detecting means is a photo electric sensor.
 7. The sheet feed assembly of claim 1 wherein said feed plate is servo driven.
 8. The sheet feed assembly of claim 3 including a servo driven nip roller.
 9. A method of feeding sheets one at a time from a stack of sheets comprising: providing feed belt/roller assembly and a feed plate moveable between a feed position and a no-feed position; driving the feed belt/roller assembly continuously during a feed cycle; and driving the feed plate between a feed position and a no-feed position.
 10. The method of claim 9 wherein said belt/roller assembly is servo driven.
 11. The method of claim 9 including providing a sheet position detecting means.
 12. The method of claim 11 wherein said sheet position detecting means is a photo electric sensor.
 13. The method of claim 10 including providing a sheet position detecting means.
 14. The method of claim 13 wherein said sheet position detecting means is a photo electric sensor.
 15. The method of claim 13 including providing a servo driven nip roller.
 16. The method of claim 9 including driving the feed plate with a servo drive. 